A report from the Wall Street Journal on Tuesday gives a much clearer look at how—and how much—information is gathered by the secret NSA programs recently brought to light in the Edward Snowden leaks. While we already knew that the NSA permitted itself to access communications “two to three hops” away from suspected terrorists (which would encompass hundreds of millions of Americans), the WSJ reports that, through the cooperation of major telecom corporations, the NSA has the ability to sample from 75 percent of the nation's Internet traffic.

The WSJ's report relies on the testimony of multiple anonymous “current and former intelligence and government officials and people from companies that help build or operate the systems, or provide data.”

These sources confirmed that, “in some cases, [the NSA] retains the written content of e-mails sent between citizens within the US and also filters domestic phone calls made with Internet technology.” Access to this information is granted at “more than a dozen” major Internet junctions on US soil, rather than sucked up exclusively from undersea or foreign cables.

As described by the paper, telecom companies send the NSA large streams of Internet traffic that are believed “most likely to contain foreign intelligence.” Then, it appears that the NSA decides what to keep from that stream based on both metadata and content of the communication, using “selectors” like e-mail addresses or IP addresses. “In making these decisions, the NSA can look at content of communications as well as information about who is sending the data,” the WSJ writes.

In one notable example, the paper described an astonishing breadth in content gathering:

For the 2002 Winter Olympics in Salt Lake City, officials say, the Federal Bureau of Investigation and NSA arranged with Qwest Communications International Inc. to use intercept equipment for a period of less than six months around the time of the event. It monitored the content of all e-mail and text communications in the Salt Lake City area.

The WSJ notes that in 2002, such surveillance was permitted due to the Bush administration's warrantless wiretapping program, “which circumvented the surveillance court on the authority of the president's power as commander in chief.” Still, current law gives surveillance a lot of leeway compared to earlier, tighter restrictions.

The WSJ article also shed some light on who hands over what when the NSA makes requests. According to one US official, the lawyers employed by telecom companies generally decide “what would be responsive.” At least one telecom company lawyer told the WSJ that the company will only provide access to “clearly foreign” data that originates in other countries.

Still, one person told the paper that the NSA has previously asked for information “likely to include domestic communication,” and that such requests “caused friction.”

”Talks between the government and different telecoms about what constitutes foreign communications have 'been going on for some years,' and ... some in the industry believe the law is unclear on Internet traffic,” the WSJ writes.